Oil-impregnated rocks of Utah: USERDA field experiment to recover oil from tar sand

The Laramie Energy Research Center, of the U. S. Energy Research and Development Administration, is equipping a field experiment to test the reverse combustion process for recovery of oil from a tar sand on a 10-acre site on the Northwest Asphalt Ridge deposit near Vernal, Utah. A tar sand section 10 feet thick at the top of the Rim Rock Sandstone (Mesaverde, Upper Cretaceous) has been selected for testing. The distribution of wells planned includes a row of 3 injection wells on both sides of a row of 3 producing wells in a 40 by 120 foot pattern to produce the estimated 1,300 barrels of oil this zone contains within the area of the test-plot. Air is to be transmitted through injection wells at 16,000 scf/hr at 200-400 psig. Production wells, with two strings of tubing, one to transmit cooling water to the bottom of the well and the other to produce hot vapors at the surface, will produce vaporized oil and water in about a 2:1 ratio by volume. Following ignition, the burning front should move from well bore into tar sand with a peak burning temperature of 800° F. The optimum air flux is 40 scf/hr-ft2 across the pattern and should result in a total production of 30-35% oil in place; 15- 2.0% will be consumed in combustion and the remainder will be deposited on the sand as coke.